Can Transcranial Magnetic Stimulation Decrease Food Reinforcement

Overview

Reduction in food reinforcement appears to be a principal way by which bariatric surgery lowers energy intake to promote weight loss and other health improvements. However, surgical modulation of mechanisms that influence food reinforcement is variable with some patients appearing more resistant to these effects than others. This "resistant" phenotype, characterized by high levels of hedonic hunger (i.e., eating for pleasure in the absence of hunger) and disinhibition (i.e., susceptibility to cues that promote overeating), can undermine surgical efficacy. Bariatric surgery patients who demonstrate this high-risk eating phenotype may benefit from strategies that can directly target neural mechanisms of food reinforcement. Repetitive transcranial magnetic stimulation (rTMS), a noninvasive procedure that delivers magnetic pulses to stimulate or inhibit nerve cells in the brain, has successfully been used to target dysregulated brain reward circuitry to diminish the reinforcing properties of addictive drugs, such as cocaine. rTMS might have a similar effect on people who have a strong drive to eat in response to the reward of palatable foods. No study has directly examined how rTMS impacts the reinforcing value of food and related brain reward processing among people who find food highly reinforcing. The reinforcing value of food can be measured by comparing how much work a person will choose to do to access that food versus an alternative reinforcer (i.e., relative-reinforcing value of food \[RRV\]). In this study, we aim to: (1) determine whether rTMS reduces the RRV relative to money; and (2) measure acute rTMS-induced modulation of reward processing with electroencephalography (EEG). Preoperative bariatric patients (n=10) will attend 2 study sessions, at least 1-week apart, with RRV and reward measures completed while EEG is collected before and after a rTMS session. With condition blinding and counterbalancing, participants will be randomized to active rTMS on one day and sham rTMS on the other day. Participants will arrive fasted in the morning, receive a standardized breakfast, complete the RRV and reward tasks during EEG before rTMS (pre-rTMS EEG), receive rTMS, then complete the RRV and reward tasks during EEG after rTMS (post-rTMS EEG). During the active condition, rTMS will be applied to the dorsolateral prefrontal cortex because this region is functionally and structurally connected to the striatum, an area necessary for reward processes. These procedures will allow for comparison of pre- to post-test rTMS changes in behavioral (RRV) and neural modulation (EEG) of food reward between the active and sham conditions.